1. Field of the Invention
This invention relates to a communication apparatus having transmission electric power control circuit, a communication apparatus having a control signal generation circuit generating a control signal indicative of compensating a table for determining a transmission power and a communication system in which transmission electric power is controlled.
2. Description of the Prior Art
A communication apparatus having transmission electric power control circuit is disclosed in Japanese patent application provisional publication No. 6-13956. In such a prior art communication apparatus, a transmission electric power is determined in accordance with an electric power of the received pilot signal. The pilot signal is detected by a mobile unit and used to estimate the power of transmission of the mobile unit. A spread spectrum communication equipment with transmission power controlled is also disclosed in Japanese patent application provisional publication No. 08032513A. In such a prior art spread spectrum communication equipment, a transmission power of a base station is determined in accordance with a detected control bit from a mobile unit.
There are two types of controlling transmission power in mobile unit communication employing the CDMA system, that is, an open loop control effected by a mobile unit in accordance with the detected electric power of the received signal and a closed loop control effected by feeding back a control signal to a mobile station from a base station.
Tomohiro Doi and Mamoru sawahashi disclosed Power control by employing Interference Power for DS/CDMA in TECHNICAL REPORT OF IEICE. A-P94-75, RCS94-99 (1994-10) at p63-68 by THE INSTITUTE OF ELECTRONICS. INFORMATION AND COMMUNICATION ENGINEERS. A transmission power at a mobile unit is controlled such that a Signal to Interference-plus-Noise power Ratio (SINR) is maintained at a constant value at a base station through a transmission power control bit (TPC bit) from the base station to the mobile unit to provide a closed loop controlling. The mobile unit increases or decreases the transmission power in accordance with the TPC bit periodically inserted in a data frame.